The missiles used in recent North Korean tests were based on the RD-250 engine once made at a plant in the city of Dnipro.
According to Michael Elleman of the International Institute for Strategic Studies, the missiles used in recent North Korean tests were based on the RD-250 engine once made at a plant in the city of Dnipro.
These could have been bought from corrupt workers and smuggled to North Korea by criminal networks, the report alleges, at some point between the collapse of the Soviet Union and Ukraine's current military crisis.
During the Soviet era, the RD-250 was produced at the Yuzhnoye design bureau's Yuzhmash plant in Dnipro, a city that is today in Kiev government-held central Ukraine, around 150 kilometers (80 miles) from a frontline held by Russian-backed separatists.
Both Ukraine and the company reacted angrily to The New York Times' account of the report, insisting that Yuzhmash has not produced military rockets since Ukraine's independence and has no links to North Korea's nuclear missile program.
But the IISS report itself does not contradict this, suggesting instead that the missile motors may have remained in storage, whether in what is now Russia or independent Ukraine, after the Soviet Union broke up.
"A small team of disgruntled employees or underpaid guards at any one of the storage sites... could be enticed to steal a few dozen engines by one of the many illicit arms dealers, criminal networks, or transnational smugglers operating in the former Soviet Union," it said.
"The engines (less than two meters tall and one meter wide) can be flown or, more likely, transported by train through Russia to North Korea."
The report includes pictures issued by Kim Jong-Un's North Korean regime which appear to show similarities between the latest missiles to be tested and the RD-250 design of a liquid-fuelled rocket.
"This is not to suggest that the Ukrainian government was involved, and not necessarily Yuzhnoye executives," Elleman wrote in the IISS report.
"Workers at Yuzhnoye facilities in Dnipropetrovsk and Pavlograd were likely the first ones to suffer the consequences of the economic misfortunes, leaving them susceptible to exploitation by unscrupulous traders, arms dealers and transnational criminals operating in Russia, Ukraine and elsewhere."
The Yuzhmash plant's marketing department said the company "has never before and does not have anything to do with North Korean missile programs of a space or defense nature."
And Oleksandr Turchynov, secretary of Ukraine's national security and defense council, seized on the report to attack Moscow, saying: "We believe this anti-Ukrainian campaign was provoked by Russian special services to cover their participation in North Korean nuclear and missile programs."